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J.F. Bell III (Cornell), Athena Science Team
Significant new information about the elemental and mineralogic composition of Mars has been provided by instruments on the two Mars Exploration Rovers. The first rover, Spirit, landed in a moderately high albedo region within a large impact crater that may once have been filled with water. Unequivocal evidence for a fluvial past has not yet been found at that site, however. Rather, the rocks at the Gusev crater landing site appear to be volcanic and/or impact in origin, with some significant compositional similarities to terrestrial volcanic materials. The second rover, Opportunity, landed within a small dark crater surrounded by the low albedo flat plains of Sinus Meridiani. The dark materials at the site contain basaltic minerals and hematite (as predicted from orbital data). More interestingly, imaging and compositional studies of an outcrop of brighter, sulfur-rich material within the Opportunity crater have provided strong evidence for the past action of liquid water at that landing site. These local rover observations are being placed into a regional and global-scale context by comparison with orbital and telescopic observations. Specifically, imaging, spectroscopic, and photometric studies of the landing sites are being made by instruments on the Mars Global Surveyor, Mars Odyssey, and Mars Express spacecraft, as well as the Hubble Space Telescope. The rover measurements, some of which are being acquired simultaneous with the orbiter measurements, provide "ground truth" information which can be used to extend and enhance the global-scale interpretation of Mars remote sensing data sets. Placing the rover results into such a global context is important for understanding the geologic and climatic evolution of Mars, as well as characterizing and selecting future landing and sample return sites.
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Bulletin of the American Astronomical Society, 36 #2
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